/*
 * px-hmac.c
 *		HMAC implementation.
 *
 * Copyright (c) 2001 Marko Kreen
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *	  notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *	  notice, this list of conditions and the following disclaimer in the
 *	  documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.	IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * contrib/pgcrypto/px-hmac.c
 */

#include "postgres.h"
#include "knl/knl_variable.h"

#include "px.h"

#define HMAC_IPAD 0x36
#define HMAC_OPAD 0x5C

static unsigned hmac_result_size(PX_HMAC* h)
{
    return px_md_result_size(h->md);
}

static unsigned hmac_block_size(PX_HMAC* h)
{
    return px_md_block_size(h->md);
}

static void hmac_init(PX_HMAC* h, const uint8* key, unsigned klen)
{
    unsigned bs, i;
    uint8* keybuf = NULL;
    PX_MD* md = h->md;

    bs = px_md_block_size(md);
    keybuf = (uint8*)px_alloc(bs);
    memset(keybuf, 0, bs);

    if (klen > bs) {
        px_md_update(md, key, klen);
        px_md_finish(md, keybuf);
        px_md_reset(md);
    } else
        memcpy(keybuf, key, klen);

    for (i = 0; i < bs; i++) {
        h->p.ipad[i] = keybuf[i] ^ HMAC_IPAD;
        h->p.opad[i] = keybuf[i] ^ HMAC_OPAD;
    }

    memset(keybuf, 0, bs);
    px_free(keybuf);

    px_md_update(md, h->p.ipad, bs);
}

static void hmac_reset(PX_HMAC* h)
{
    PX_MD* md = h->md;
    unsigned bs = px_md_block_size(md);

    px_md_reset(md);
    px_md_update(md, h->p.ipad, bs);
}

static void hmac_update(PX_HMAC* h, const uint8* data, unsigned dlen)
{
    px_md_update(h->md, data, dlen);
}

static void hmac_finish(PX_HMAC* h, uint8* dst)
{
    PX_MD* md = h->md;
    unsigned bs, hlen;
    uint8* buf = NULL;

    bs = px_md_block_size(md);
    hlen = px_md_result_size(md);

    buf = (uint8*)px_alloc(hlen);

    px_md_finish(md, buf);

    px_md_reset(md);
    px_md_update(md, h->p.opad, bs);
    px_md_update(md, buf, hlen);
    px_md_finish(md, dst);

    memset(buf, 0, hlen);
    px_free(buf);
}

static void hmac_free(PX_HMAC* h)
{
    unsigned bs;

    bs = px_md_block_size(h->md);
    px_md_free(h->md);

    memset(h->p.ipad, 0, bs);
    memset(h->p.opad, 0, bs);
    px_free(h->p.ipad);
    px_free(h->p.opad);
    px_free(h);
}

/* PUBLIC FUNCTIONS */

int px_find_hmac(const char* name, PX_HMAC** res)
{
    int err;
    PX_MD* md = NULL;
    PX_HMAC* h = NULL;
    unsigned bs;

    err = px_find_digest(name, &md);
    if (err)
        return err;

    bs = px_md_block_size(md);
    if (bs < 2) {
        px_md_free(md);
        return PXE_HASH_UNUSABLE_FOR_HMAC;
    }

    h = (PX_HMAC*)px_alloc(sizeof(*h));
    h->p.ipad = (uint8*)px_alloc(bs);
    h->p.opad = (uint8*)px_alloc(bs);
    h->md = md;

    h->result_size = hmac_result_size;
    h->block_size = hmac_block_size;
    h->reset = hmac_reset;
    h->update = hmac_update;
    h->finish = hmac_finish;
    h->free = hmac_free;
    h->init = hmac_init;

    *res = h;

    return 0;
}
